Fluid-working machines



W. W. WHITE March 7, 1967 FLUIDWORKING MACHINES Filed April 15, 1965 WmM? w w L W M4 A$JM m a W United States Patent 3,307,776 FLUID-WORKIN GMACHINES William W. White, Glasgow, Scotland, assignor to James Howden &Company Limited, Glasgow, Scotland Filed Apr. 15, 1965, Ser. No. 448,328Claims priority, application Great Britain, Apr. 15, 1964, 15 ,5 64/ 642 Claims. (Cl. 230--127) This invention relates to centrifugal machinessuch as centrifugal mixed flow, single and double inlet fans, andcentrifugal blowers, pumps and compressors. The present invention isconcerned with the kind of centrifugal machine which comprises a casinghaving a pair of spaced side walls, an impeller rotatable in the casingbetween the side walls and having its inlet side spaced from a side wallto define therewith an annular space into which high pressure fluidleaks from the impeller outlet, an inlet opening in said side wall, andan inlet conduit extending within the casing from the inlet opening andat its inner end forming with the impeller inlet an annular leakageorifice, the annular space opening into the annular orifice so that highpressure leakage fluid flows from the annular space axially through theannular orifice into .the impeller.

The object of the invention is to improve a centrifugal machine of theaforesaid kind in a simple and inexpensive manner.

According to the present invention, we provide a peripheral series ofaxially extending guide vanes on the exterior of the inlet conduit toguide and stabilize the leakage flow of fluid through the annular spacetowards the annular orifice.

Each guide vane may extend axially in a radial plane containing themachine axis, or may be curved or sloped transversely of said plane. Itis found that guidance of the leakage flow by the vane means results inan increase in machine efiiciency and an increase in the stability ofthe machine performance curve relating pressure rise to volume flow.

An embodiment of the invention will now be described by way of examplewith reference to the accompanying diagrammatic drawing in which FIG. 1is a sectional elevation of a single-inlet centrifugal fan, and FIGS. 2to 4 are detail views showing modifications of the fan of FIG. 1.

Referring to the drawings:

A single-inlet centrifugal fan consists of a single-suction impeller 1mounted within a volute casing 2 on a shaft 3 which extends through oneside wall 4 of the casing and is secured to the adjacent side wall 5 ofthe impeller. The other side wall 6 of the impeller 1 is spaced from theother side wall 7 of the casing 2 to define with the wall 7 an annularspace S through which high pressure fluid leaks from the impeller outlettowards the impeller inlet. The side wall or shroud 6 of the impeller isof substantially frusto-conical form and is outwardly convergent,terminating at its inner diameter in a cylindrical rim 8 defining theinlet eye of the impeller. The casing side wall 7 adjacent to and spacedfrom the inlet eye has an entry opening 9 therein, and a venturi-sectionconduit 10 fixed to the side wall 7 projects inwards from said opening 9and terminates at its inner end within the cylindrical rim 8 so as toguide entry fluid through the casing 2 to the inlet eye. The conduit 10may consist of a frustoconical inlet portion 11, and a radiused portionmerging smoothly into the inlet portion and constituting a throat3,307,776 Patented Mar. 7, 1967 12 and flared outlet 13. There is anannular passage 14 between the inner end of the conduit 10 and the boreof the rim 8 of the impeller to permit free rotation of the impeller,and in operation of the fan there is a free leakage flow of highpressure fluid from the impeller outlet, through the space S and annularpassage 14 into the impeller, as indicated by the arrows L. A peripheralseries of say 3 to 10 equispaced radial guide vanes 15 are secured tothe exterior of the conduit 10, e.g. by welding, and extend over a majorportion of the conduit length. The vanes top edges 15A are substantiallyparallel to the outer face of the conduit 10, and the vanes terminateshort of the conduits inner end so that the inner ends of the vanes arespaced outwards from the end of the rim, as shown.

In the modification according to FIG. 2, the inner ends of guide vanes16 terminate at or near the inner end of the conduit 10, so that endportions 16A of the vanes lie within the rim 8.

In the modification according to FIG. 3, the guide vanes 17 arerelatively short and transversely curved, and are located upstream ofthe throat 12 of the conduit 10.

In the modification according to FIG. 4, the vanes 18 are relativelyshort, extending over the throat 12 and flared outlet 13 of the conduit10, and with their top edges 18A substantially parallel to the fan axis.

In use of the fan, the guide vanes serve to guide and stabilize theleakage flow L of fluid in the zone S of the volute casing 2 around theconduit 10. When used with suitable impellers, the guide vanes insuitable number, shape, and location are found to give a marked increasein the fan efficiency and also an increase in the stability of the fanperformance curve relating pressure rise to volume flow.

I claim:

1. In a centrifugal fan comprising a casing having a pair of spaced sidewalls, an impeller rotatable in the casing between the side walls andhaving its inlet side spaced from a side wall to define therewith anannular space into which high pressure fluid leaks from the impelleroutlet, an inlet opening in said side wall, and an inlet conduitextending within the casing from the inlet opening and at its inner endforming with the impeller inlet an annular leakage orifice, the annularspace opening into the annular orifice so that high pressure leakagefluid flows from the annular space axially through the annular orificeinto the impeller; a peripheral series of axially extending guide vaneson the exterior of the inlet conduit to guide and stabilize the leakageflow of fluid through the annular space towards the annular orifice.

2. In a centrifugal fan comprising a casing having a pair of spaced sidewalls; an impeller rotatable in the casing between the side walls andhaving its inlet side spaced from a side wall to define therewith anannular space into which high pressure fluid leaks from the impelleroutlet, and having an inlet which is defined by a cylindrical rimcoaxial with the impeller; an inlet opening in said side wall; and aventuri section inlet conduit extending within the casing from the inletopening and terminating within the cylindrical rim to define therewithan annular passage, the annular space opening into the annular passageso that high pressure leakage fluid flows from the annular space axiallythrough the annular passage into the impeller; a peripheral series ofaxially extending guide vanes on the exterior of said inlet conduit toguide and stabilize'the fluid flow through the annular 2,143,100 1/ 1939Anderson 230128 space towards the annular passage. 2,656,096 10/ 1953Schwarz 2301 14 FOREIGN PATENTS References the Examiner 5 Canada. UNITEDSTATES PATENTS 1,200,157 6/ 1959 France.

710,391 7 6/ 1954 Great Britain. 5/1906 Guy 230122 10/ 1910 Krogh103-103 DONLEY J. STOCKING, Primary Examiner. 10/1927 Burns 230127 10HENRY F. RADUAZO, MARK NEWMAN,

1/ 1931 Anderson 230122 Examiners.

1. IN A CENTRIFUGAL FAN COMPRISING A CASING HAVING A PAIR OF SPACED SIDEWALLS, AN IMPELLER ROTATABLE IN THE CASING BETWEEN THE SIDE WALLS ANDHAVING ITS INLET SIDE SPACED FROM A SIDE WALL TO DEFINE THEREWITH ANANNULAR SPACE INTO WHICH HIGH PRESSURE FLUID LEAKS FROM THE IMPELLEROUTLET, AN INLET OPENING IN SAID SIDE WALL, AND AN INLET CONDUITEXTENDING WITHIN THE CASING FROM THE INLET OPENING AND AT ITS INNER ENDFORMING WITH THE IMPELLER INLET AN ANNULAR LEAKAGE ORIFICE, THE ANNULARSPACE OPENING INTO THE ANNULAR ORIFICE SO THAT HIGH PRESSURE LEAKAGEFLUID FLOWS FROM THE ANNULAR SPACE AXIALLY THROUGH THE ANNULAR ORIFICEINTO THE IMPELLER; A PERIPHERAL SERIES OF AXIALLY EXTENDING GUIDE VANESON THE EXTERIOR OF THE INLET CONDUIT TO GUIDE AND STABILIZE THE LEAKAGEFLOW OF FLUID THROUGH THE ANNULAR SPACE TOWARDS THE ANNULAR ORIFICE.